1. Field of the Invention
The present invention relates to a component of a wireless IC device including a wireless IC for use with an RFID (Radio Frequency Identification) system, and also relates to the wireless IC device.
2. Description of the Related Art
Recently, as an article management system, an RFID system has been developed in which communication is performed between a reader/writer that generates an induced electromagnetic field and an IC chip (also referred to as an IC tag, a wireless tag, or a wireless IC chip) with a non-contact method so that information is transferred, the IC chip including predetermined information stored therein and being provided in an article, a container, or other object. It is possible for an IC chip, as a result of being connected to an antenna, that is, a radiation plate, to communicate with a reader/writer. As a wireless tag including an IC chip provided therein, a wireless tag is disclosed in Japanese Unexamined Patent Application Publication No. 2005-244778.
This wireless tag is defined by an IC chip and includes a main antenna element arranged on either side of the IC chip, a matching unit disposed between the IC chip and the main antenna element, and an auxiliary antenna element arranged in proximity to the inner side end surface of the main antenna element. In such a wireless tag, the matching unit matches the impedance of the IC chip to that of the main antenna element, and transmission and reception of a signal is performed by the main antenna element, thereby functioning as a wireless tag.
However, in the wireless tag, since the matching units arranged on the sides of the IC chip are arranged in a planar configuration on a dielectric substrate, an electromagnetic field generated in the matching units extends outside of the dielectric substrate. For this reason, when the wireless tag is laminated on an article, the dielectric constant in the vicinity of the matching units is changed, thereby causing the inductance value and the capacitance value of the matching units to be changed, and the matching state between the IC chip and the main antenna element is changed. As described above, if the matching state between the IC chip and the main antenna element is changed, desired radiation characteristics are not obtained in the main antenna element, and a communication problem occurs with the reader/writer that performs wireless communication with the wireless tag, which presents a problem in that the operation of the wireless tag is unstable.
Furthermore, in the wireless tag, another problem is that since matching units are arranged on the sides of the IC chip on a dielectric substrate, the size of wireless tag is increased.
Furthermore, in the wireless tag, since an IC chip is arranged so as to be viewable externally on a dielectric substrate, after a wireless tag is laminated on an article, there is a possibility that the IC chip contacts another article when the article is moved or carried, which presents another problem in that the IC chip may be damaged or may detach from the dielectric substrate due to impact, and thus, the wireless tag does not operate as a wireless tag. Furthermore, another problem is that when the IC chip is exposed to the outside, corrosion due to temperature and humidity in the periphery of the wireless tag, or other environmental factors occurs and the environmental resistance performance of the wireless tag is poor.